In the oilfield industry, various downhole tools (e.g., packers, bridge plugs, frac plugs) may be used to isolate sections of a wellbore. Such downhole tools may include a sealing element, which is generally made of rubber, and slips configured to bite into a surrounding tubular and maintain a position of the tubular in the wellbore. The sealing element and slips may initially be in a contracted configuration, allowing the downhole tool to be run into the wellbore without engaging the wellbore or any other surrounding tubular.
Upon reaching a desired location, such as an interface between two formation zones, the tool may be set. As part of the setting process, the slips and the sealing element may be expanded so as to engage the surrounding tubular (e.g., casing, liner, wellbore wall), which may provide the desired zonal isolation.
Such downhole tools may be retrievable or non-retrievable. In the latter case, the tools are generally removed by drilling them out. With retrievable tools, on the other hand, a retrieval tool may be provided that attaches to the wireline (or another suitable line), which may engage with the downhole tool. Using the retrieval tool, the sealing element and the slips may be disengaged from the surrounding tubular and pulled out of the wellbore.
In use, a large pressure differential may develop across the downhole tool. At some point, this pressure differential may cause the downhole tool to fail. Such failure may be caused by the slips applying an insufficient holding force, the sealing elements failing to provide a seal, or by shearable elements of the downhole tool's setting assembly failing under this pressure.